Abstract: An apparatus for detecting an approaching train within a track section utilizes a transmitter coupled to the rails at a feed point for applying a current to the track section. There is a receiver coupled to the track section for producing a signal representative of the impedance of the track section. There are devices for utilizing the received signal for detecting train motion, abnormally low impedance and abnormally high impedance of the track section. A normalizer circuit is connected to the receiver for increasing or decreasing the received signal gain within predetermined limits in accordance with variation in impedance of the track section.
Type:
Grant
Filed:
April 17, 1975
Date of Patent:
March 16, 1976
Assignee:
Saftran System Corporation
Inventors:
James E. Moe, Richard V. Peel, Richard E. Smith